There are a variety of instances where an ocular implant is inserted into the anterior chamber, posterior chamber, cornea, vitreous space and/or other portion of an eye. Exemplary ocular implants include, but are not limited to, lenses, capsular tension rings, ocular prosthesis and lamellar transplants. An intraocular lens (IOL), for example, may be inserted into an aphakic eye that has undergone a cataract surgery or may be inserted into a phakic eye during a refractive surgery. One type of lens is a foldable lens. Foldable lenses are formed from soft material such as silicone, soft acrylic, or hydrogel and may inserted into the eye through a small incision. Lens insertion apparatus, which may be used to push a foldable lens into an eye through a small diameter insertion tube, generally include push-type apparatus and screw-type apparatus. In both cases, the lens insertion apparatus may include a plunger with a rod that is used to push the lens through the insertion tube, and an operational portion that is used to drive the rod.
During use of push-type lens insertion apparatus, the operator presses the operational portion against a resistance, such as the friction between the lens and the inner wall of insertion tube, to move the rod and lens through the insertion tube. One example of such an apparatus is disclosed in Japanese Unexamined Pat. App. Pub. No. 2000-516487 (also published as U.S. Pat. No. 5,766,181). Although such push-type apparatus are advantageous in that they may be operated with one hand, precise control of the lens movement through the insertion tube can be difficult to achieve because the pressure applied to the operational portion by the operator must be balanced against frictional resistance. This can be problematic because folded lenses, which are under a large load as they are compressed through the insertion tube, especially in those instances where the optical portion of the lens is thick or the insertion tube has a relatively small inner diameter, spring back to their unstressed shape as they exit the insertion tube. Unexpected release of the lens into the eye can, therefore, result in damage to ocular tissue. Some push-type lens insertion apparatus, such as that disclosed in Japanese Unexamined Pat. App. Pub. No. H11-510711 (also published as PCT Pub. No. WO 96/37152), are configured such that the resistance increases as the lens is pushed distally.
In screw-type lens insertion apparatus, threads are used to connect the operational portion to the main body. Rotation of the operational portion results in linear movement of the plunger rod and lens in the distal (or “lens advancing”) direction. With such apparatus, one example of which is disclosed in Japanese Unexamined Pat. App. Pub. No. H11-506357 (also published as. PCT Pub. No. WO 96/28122), the travel distance of the plunger rod can be easily controlled, thereby preventing the unexpected release of the lens into the eye. Screw-type lens insertion apparatus are, however, more difficult to operate than push-type lens insertion apparatus because operation of the screw-type lens insertion apparatus requires two hands. Screw-type lens insertion apparatus are also structurally more complicated.
Attempts have also been made to harness the advantages of the above-mentioned push and screw-type lens apparatus, while avoiding the disadvantages, in a single apparatus. In the apparatus disclosed in Japanese Unexamined Patent Application Publication No. H5-103809, for example, a rotating mechanism may be used to control the travel distance of the plunger in a push-type apparatus. The ability of the apparatus to switch from push-type operation to screw-type operation is, however, dependent upon the behavior of the lens within the nozzle and may not be available at the time desired. Although the screw-type lens insertion apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2003-210498 (also published as U.S. Pat. No. 6,666,871) may be operated with both hands, or with only one hand, the operational portion or its component for moving the plunger forward must be carefully operated to prevent unintended rotation. The operational portion also rotates as it is pushed distally, which the present inventor has determined is both distracting and unnecessary.
Accordingly, the present inventor has determined while lens insertion apparatus that can provide both push-type operation and screw-type operation are desirable, those currently available are susceptible to improvement.